A medical student performs carotid sinus massage on a classmate. Within seconds the heart rate falls from 75 to 55 bpm. The afferent limb of this reflex travels in which nerve?

• A Vagus nerve
• B Hypoglossal nerve
• C Glossopharyngeal nerve ✓
• D Sympathetic cardiac nerves

Explanation

Baroreceptors of the carotid sinus send their afferent fibres through the carotid sinus branch of the glossopharyngeal nerve (Hering's nerve) to the nucleus tractus solitarius. The efferent limb then runs in the vagus to the SA node, increasing M2-mediated slowing. The aortic arch baroreceptors are the ones whose afferents travel in the vagus, which is the key distractor distinction here.

Reference: Ganong Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.